Lecture 7: Synaptic Transmission Flashcards
What is the synaptic cleft?
Space between the presynaptic neuron and the postsynaptic neuron or effector organ.
What are the steps to synaptic transmission?
- AP arrives at the axon terminal of presynaptic neuron.
- Triggers voltage gated calcium channels to open.
- This triggers exocytosis of neurotransmitters from vesicles into synaptic cleft.
- Binds to receptors of postsynaptic neuron or effector organ.
- Ligand gated receptors causes ligand gated channels to open.
What happens in the neuron to neuron synapse?
Postsynaptic graded potentials result in depolarization or hyperpolarization of the membrane potential.
How to end a neurotransmitter’s effect on a postsynaptic neuron or effector organ?
- Reuptake by presynaptic neuron.
- Degradation by enzymes.
- Diffusion away from synaptic cleft.
What is temporal summation?
It is when a post synaptic neuron receives more than one EPSP in a short period of time. Since usually one is not enough to conduct an AP.
What is the difference between excitatory and inhibitory post synaptic potentials?
Excitatory: Sodium ions flow in the neuron causing depolarization and resulting in AP.
Inhibitory: Potassium ions flow out or chlorine ions flow in which result in hyperpolarization and reduce chances of AP.
What is spatial summation?
It is when a neuron receives multiple messages (some inhibitory and excitatory) from different neurons at the same time.
What are the six important neurotransmitters?
- Acetylcholine (ACh)
- Norepinephrine (NE)
- Dopamine
- Serotonin
- Glutamate and GABA
- Endorphins
What is the importance of acetylcholine in brain and PNS?
Brain: Located around the lower cerebrum and midbrain. it is involved in memory, cognition and sleep formation. (Alzheimer’s disease) (Hippocampus)
PNS: Stimulates our skeletal muscles to contract (voluntary)
Used by motor neuron in autonomic pathways as well.
What is the importance of norepinephrine in the brain and PNS?
Neurons that produce NE are clustered within the reticular formation. Allows for level of alertness and consciousness.
PNS: Released by sympathetic motor neurons at synapses with effector organs. (increasing heart rate, blood pressure and blood flow to muscles).
What is the importance of dopamine?
It is associated with reward motivated behaviors. It also helps with smooth and coordinated movements. Lack of dopamine results in tremors and difficulty moving (Parkinson’s disease).
What is the importance of serotonin?
Provides help with mood regulation and contributes to happiness and well being. Also used in the digestive system to promote intestinal function.
Which are the three neurotransmitters that are associated to mood stability?
Dopamine, norepinephrine and serotonin
What is the importance of GABA and Glutamate?
Glutamate: Used in excitatory synapses in the brain.
GABA: Used in inhibitory synapses in the brain.
(Note: Increased glutamate can lead to seizures)
What is the importance of endorphins?
Signaling molecules that are produced and released in the brain that have pain relieving and stress relieving properties that are similar to morphine.
What is a psychoactive drug?
Drugs that can cross the blood brain barrier and affect our mood or emotional state.
What is the difference between an agonist and an antagonist?
Agonist: Increases the action of a neurotransmitter.
Antagonist: Decreases the action of a neurotransmitter.
What are the five different ways in which agonists and antagonists can act?
- Stimulate the release of a neurotransmitter.
- Prolong the effect of neurotransmitter already released.
- Mimic the effect of a neurotransmitter.
- Inhibit the release of a neurotransmitter.
- Block a neurotransmitter from binding to it’s receptor.
What are selective serotonin re-uptake inhibitors? (SSRIs)
SSRIs are serotonin agonists in which they block serotonin reuptake by transporters in the presynaptic axon terminal which extends it’s effect.
What is nicotine?
An acetylcholine agonist that binds to certain types of ACh receptors.
Effect in the CNS: Increases focus and releases dopamine.
Effect in the PNS: Increases heart rate and blood pressure.
What is marijuana?
Psychoactive ingredient is THC (and CBD) which mimics the effect of certain neurotransmitters in the brain.
What is alcohol?
It is a depressant (suppresses the nervous system).
Neurotransmitter antagonist which leads to loss of motor control, concentration, balance and coordination.
What are opiates?
Block neurotransmitters that allow us to perceive pain and fear.
Breathing rate slows resulting in death due to overdosage.
What is drug tolerance?
Progressive decrease in the effectiveness of a drug in a given person.
